An EPA investigation found Hyundai Motor Co. and Kia Motors Corp issued inflated fuel economy ratings for about 900,000 vehicles sold in the U.S. since late 2010.

The auto companies, which are both owned by Hyundai Motor Group, will lower the fuel economy ratings for about 35 percent, or 900,000, of the 2011-2014 model year vehicles sold through October 31, 2012 in the U.S. Hyundai issued a similar statement that about 172,000 vehicles sold in Canada also had incorrect gas mileage data.

The EPA said Friday the mileage on most vehicle labels will be reduced by one to two miles per gallon. The largest adjustment will be for the Kia Soul, which was off by as much as 6 mpg on the highway and 3 mpg in the city. The changes will reduce the fuel economy of the entire 2012 Hyundai/Kia fleet from 27 miles per gallon to 26 mpg, Hyundai said.

Both automakers will relabel vehicles currently in showrooms. Customers will receive a personalized debit card that will reimburse them for their difference in the EPA combined fuel economy rating, based on the fuel price in the customer's area and their own actual miles driven, Hyundai said. Hyundai will add an extra 15 percent to the amount in acknowledgement of its error and current owners will be able to refresh the debit card for as long as they own the vehicle.

Hyundai did not provide an estimate on the cost of compensating current and former customers. However, it will most likely cost millions of dollars.

The EPA opened an investigation into Hyundai and Kia after receiving a number of consumer complaints about the mileage estimates. EPA initially discovered discrepancies between results from testing of a 2012 Hyundai Elantra and data submitted by the automaker. The EPA later expanded its investigation into other Hyundai and Kia vehicles.

EPA routinely tests between 150 to 200 vehicles a year--or about 15 percent of the possible vehicles configurations--at its National Vehicle and Fuel Emission Laboratory in Ann Arbor, Mich., to ensure performance matches the mileage and emissions data submitted by automakers.

Kirsten Korosec has written for Technology Review, Marketing News, The Hill, BNET and Bloomberg News. She holds a degree from Northwestern University's Medill School of Journalism. She is based in Tucson, Arizona.
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